Angels do take human form at times. Whether they do so to help out an individual in a crisis I can't be sure. Rememeber, we're given a free will, and there would be a very fine line between that will and it's consequences and divine intervention to prevent us from making mistakes.
Well God can certainly have angels appear in many forms, if He so chooses. And yes, correcting/preventing all of our mistakes is certainly not job one for them.